Defiant daylight adjusting digital timer backlight will not stay on

Within the last 2 years I purchased and installed two defiant backlit LED timers and they work great. I also like that the backlit LED stays lit on both at all times. However, I recently bought what I thought was the same timer and installed it on another switch. However, on this one the LED backlight does not stay on, though the LED display continuously shows the time, etc., as it should in clock mode. The Backlight stays on while pressing buttons and setting up the timer, but the light goes off after about 15 seconds following any button punches. Otherwise the timer works great. Is there a way to set the LED backlight so it will stay on full time?